Go on a water safari (complete with wetsuit, mask and snorkel), and watch these wonderfully inquisitive creatures swim up and away and up again, trying to work out who you are and what the blazes you're doing here. Shy at first, seals soon get used to you being in the water and dash about hunting and playing around you. Young pups explore with their mouths, so tend to nibble at fins, masks and cameras. If they get very confident, they may even rub their bodies on you. Aaaaaah!

What's the buzz?

It is always wonderful to see another species in its own environment - but this is all the more exciting because you are in the sea. Keep in contact with other people in the water, else you might find the seals swim up behind you without you even noticing them.

Thrill a minute?

You have to get a boat out to most of the seal colonies in the UK, and then usually only get an hour or two in the water before turning back. There again, it is quite tiring being in the water for that long, especially if you make the mistake of trying to "chase" the seals (they can reach top speeds of 20mph, which makes them rather hard to follow). It can also get quite cold, especially if it's not sunny.

Adrenaline peak

When that first seal comes up close and looks you right in the eye, it can be quite an intense and emotional experience. The interaction with them is fantastic - by comparison, encounters with other marine life in the UK (basking sharks and dolphins, for example) tend to be fleeting at best. With seals, you are almost guaranteed a close encounter as they live in colonies, stay in the same place, and don't seem to mind people being in the water near them at all.

Where to do it

The UK is home to half the world's population of grey seals. There are colonies on the Isles of Scilly, on remote North Rona in Scotland, Blakeney Point in Norfolk, the Farne Islands in Northumberland and Lundy Island in the Bristol Channel, to name but a few. Many local boats offer sightseeing trips only, rather than the opportunity to get in the water with our grey friends, so check with local tourist offices for information on boats that do swimming trips.

Who can do it

Skippers prefer to take people with some snorkelling experience. You'll be in the water for a good while, so you must also be a confident sea swimmer.

What to take

Check with the boat's skipper, as some provide only masks and snorkels. You'll want to hire a wetsuit and probably fins, too, to save your legs doing too much work. And do get hold of an underwater camera (there are even disposable ones) to capture the encounters.

Typical prices

£40 per person for the boat and (some) equipment hire.

Impress your pals

Seals can dive as deep as 200 metres for 30 minutes at a time - at which point their heart rates slow from 120 beats a minute to just four or five. The grey seal's scientific name, Halichoerus grypus, derives from the Greek words meaning "hook-nosed sea pig".

Fishing sharks out of the sea might not sound like the most eco-friendly adventure, but shark tagging has the backing of the World Wildlife Fund for Nature (WWF) and gives a select few volunteers the chance to imitate Roy "we're gonna need a bigger boat" Scheider - while doing their bit for the conservation of Britain's declining shark population.

The UK Shark Tagging Programme, set up by the National Oceanography Centre in Southampton, has enlisted a nationwide fleet of experienced sea anglers to help monitor the behaviour of Britain's sharks - even including the odd hammerhead. These skippers sometimes require extra volunteers - but note this is very tough and physical work.

Boats head out to sea at either dusk or dawn, when sharks are usually feeding. They are enticed to swim close by the creation of a "chum slick", a foul-smelling concoction of old mackerel blood, guts and oil that is slung overboard. Fresh mackerel is then attached to lines of varying length on heavy-duty rods with special (damage-limiting) circle hooks. If and when a shark takes, landing it can still be a difficult and long struggle, even for an experienced sea angler. And once the shark is on board it'll thrash about, of course, making the task of fixing the tag to its dorsal fin rather tricky.

Furthermore, sharks have very delicate insides so there are strict guidelines for handling them. Once tagged, the shark is released back into the water. If it is recaptured in the future, the tag number and location is recorded, enabling a picture of the sharks' movements and breeding patterns to be built up. This should, in time, ensure that trawlers and long-line fishing vessels are kept away from Britain's - indeed Europe's - most sensitive shark-infested waters.